Carbohydrate attachment sites

Fig. 2. Schematic diagram of the three pairs of polypeptide chains of fibrinogen. The Aa, B/3, and 7 chains are represented by bars with lengths proportional to the number of amino acid residues in each chain and the N- and C-terminal ends of the chains are labeled. The coiled-coil regions are indicated by the diagonally striped boxes, while the intra- and interchain disulfide bonds are indicated by solid lines. Carbohydrate attachment sites are labeled with CHO, while thrombin and major plasmin cleavage sites are indicated by T and P, respectively. (Adapted from Fig. 12-1 of Hantgan et al., 2000.)...

Fig. 7. (A) A detailed model of the amino-terminal al(IV) and a2(IV) chains containing the 7 S domain and an adjacent segment of the main triple helix. The terminal sequence of both chains is nonhelical and contains lysines (K), hydroxylysines (K), and cysteines (C) that participate in intra- and intermolecular cross-linking. A helical cross-linking site is located about 30 nm from the amino terminus (N) of the molecule and contains cysteines and a hydroxylysine in the al(IV) chain involved in cross-linking plus a complex carbohydrate attachment site (CHO). The cap site within the main triple helix identifies a series of four triplets containing proline (P) and hydroxyproline (P), a composition that would be expected to form a very stable helical structure, [Data from Glanville et al. (1985) Siebold et al. (1987)]. (B) The antiparallel arrangement of type IV molecules with alignment of cross-linking sites.

Fig. 10. (A) Proteolytic fragments derived from laminin and activities found to be associated with them. (B) A domain model for the B1 chain of mouse laminin deduced from the nucleotide structure of cDNA clones. Domains 1 and II are largely helical and probably form a coiled-coil structure with a similar portion of the B2 chain. There are several possible carbohydrate attachment sites. These domains are separated by a region a" containing six cysteines closely bunched, possibly involved in cross-linking to the B2 and A chains. Domains III and V are cysteine-rich regions composed of repetitive segments of about 50 amino acids each. These domains may form the two rod-like elements within the short arm, whereas domains IV and VI are thought to form the visible globular structures.

Modification ofAA4 and AA5 The phenolic group of " Hpg serves as the carbohydrate attachment site, and in semisynthetic approaches, this group has been deriva-tized by protecting groups. Besides these modifications, other glycopeptide derivatives do not exist. This is similarly the case for Hpg, where some naturally occuring derivatives are known, which are chlorinated in the o-position of the... 

Two calcium ion binding sites have been identified in the protein, one on the four-fold symmetry axis near the outermost surface of the tetramer, and one approximately 8 A from the active site. Calcium has been shown to increase the catalytic rate of the enzyme, although it is not absolutely necessary for activity [21,22]. Four carbohydrate attachment sites have also... 

Three-dimensional structure of lactotransferrin. Top schematic representation of the folding pattern of each lactoferrin lobe Domain I is based on a beta-sheet of four parallel and two antiparallel domains Domain II is formdd from four parallel and one antiparallel strand. Bottom stereo Ca diagram of the N lobe of lactoferrin ( ) iron atom between domain I (residues 6-90-I-) and domain II (residues 91-251) ( ) disulfide bridges ( ) carbohydrate attachment site. See Reference 39. 

Fig. 26.11 The rationale behind the 2Fq - Fc maps. Shown is a carbohydrate attachment site at Asn109 in human leukocyte elastase. The carbohydrate chain has not been added to the model. The Fq map in (a) mainly shows the electron density of the model, owing to the model bias. Some electron density is present for the carbohydrate, but it is very weak and not connected to the Asn residue. The Fo - Fc map in (b) shows only features which have not been accounted for in the model, in this case the carbohydrate moiety. The 2Fo - Fg map in (c) is a combination of the two and shows both density belonging to the model and strong connected density for the carbohydrate. From these figures, it is clear why crystallographers prefer a 2Fo - Fc map over an Fq map.

Crossin, K. L., Edelman, G. M., and Cunningham, B. A., 1984, Mapping of three carbohydrate attachment sites in embryonic and adult forms of the neural cell adhesion molecule, J. Cell Biol. 99 1848-1855. 

Fig. 3. Human CG, hLH, and equine CG (eCG) P-subunits. Amino acid numbeiing is relative to maximum homology between the three subunits. Consensus glycosylation sites ate at Asn-13 and 30. = same amino acid as hCG/3. Underlined Asn residues indicate attachment of N-linked carbohydrate chains. Serines at positions 121, 127, 132, and 138 of hCGP are underlined to indicate sites of O-linked carbohydrate attachment. Residues 115—118,...

Figure 5.1 Schematic diagram of the lactoferrin molecule. The positions of carbohydrate attachment are marked with a star. O, ovotransferrin T, human serotransferrin L, human lactoferrin R, rabbit serotransferrin M, melanotransferrin A, the connecting helix B, the C-terminal helix. The disulfide bridges are indicated by heavy bars, and the iron and carbonate binding sites by filled or open circles, respectively. Reprinted from Baker et al., 1987. Copyright (1987), with permission from Elsevier Science.

Studies of other sources of ceruloplasmin may eventually prove useful in structure elucidation, but have already clarified some of the copper chemistry. Ceruloplasmin from goose serum has been isolated, purified, and characterized. This ceruloplasmin has less carbohydrate attached, but two forms may be isolated under some conditions. It is clear that these are not products of proteolytic degradation, but perhaps they might have a different carbohydrate attached. The two type I sites have higher extinction coefficients than type I sites in other ceruloplasmins, reflecting a modestly different environment (Hilewicz-Grabska et al, 1988). 

In many receptors, the extracellular domain contains the hgand binding site. Glycosy-lation sites, i.e., attachment sites for carbohydrate residues, are also located nearby in the extracellular domain. 

For the porcine and rat enzymes only the differences from the bovine enzyme are shown. The sites of carbohydrate attachment in the porcine enzyme are shown by the residues in full capital letters (Asn, 21, 34, and 76). For all the enzymes the four disulfide groups are paired in the same way, 26-84, 40-95, 58-110, and 65-72. 

Fig. 1. The GP Ib-IX-V complex. The complex consists of seven transmembrane polypeptides denoted GP Iba (mol wt 145,000), GP Ibp (mol wt 24,000), GPIX (mol wt 17,000) and GP V (mol wt 82,000), in a stoichiometry of 2 2 2 1. The hatched region represents the plasma membrane. The area above the hatched region represents the extracellular space that below represents the cytoplasm. The complex is a major attachment site between the plasma membrane and the cytoskeleton. Two molecules associated with the cytoplasmic domain are depicted a 14-3-3 dimer, which may mediate intracellular signaling, and actin-binding protein, which connects the complex to the cortical cytoskeleton and fixes its position and influences its function. The dark circles represent O-lihked carbohydrate and the dark squares represent IV-linked carbohydrate. Both types of carbohydrate are added after...

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